bio 8

Although in humans there are 22 pairs of autosomal chromosomes, only three different chromosomal trisomies are commonly seen in newborns. Of the remaining 19 autosomes, many trisomies have not been seen in newborns. Why not? Although in humans there are 22 pairs of autosomal chromosomes, only three different chromosomal trisomies are commonly seen in newborns. Of the remaining 19 autosomes, many trisomies have not been seen in newborns. Why not? a) Trisomy for the other autosomal chromosomes is often lethal, and the affected embryos are miscarried. b) These autosomal chromosomes do not contain the same type of DNA or protein that makes up chromosomes susceptible to trisomy. c) Trisomy for these other autosomal chromosomes occurs so rarely that it has never been documented. d) Trisomy for these autosomal chromosomes has no effect and therefore would never be noticed.

a

Each somatic cell in an individual with Down syndrome contains _____ chromosomes. a) 47 b) 46 c) 24 d) 45

a

If a fragment of a chromosome breaks off and then reattaches to the original chromosome at the same place but in the reverse direction, the resulting chromosomal abnormality is called _____. a) an inversion b) a reciprocal translocation c) a deletion d) a nondisjunction

a

Karyotyping a) can reveal alterations in chromosome number. b) shows chromosomes as they appear in metaphase of meiosis II. c) examines points of crossing over. d) reveals the presence of cancerous genes.

a

A karyotype is most like a) a map showing the hidden location of buried treasure. b) a movie showing the stages of the reproductive cycle of a beetle. c) the answer key to a multiple-choice exam. d) photographs of every couple at a high school prom.

d

According to the graph, at what maternal age is the incidence of Down syndrome equal to five times the incidence at age 40? a) about 29 or 30 b) about 35 or 36 c) about 44 or 45 d) about 46 or 47

d

Consider the photograph of a karyotype. This is _____. a) an individual's physical traits b) a means of determining a person's phenotype c) all the possible gametes a person could produce d) a photograph of all a person's chromosomes

d

During meiosis, homologous chromosomes sometimes "stick together" and do not separate properly. This phenomenon is known as _____. a) nondisjunction b) sticky chiasmata c) meiotic failure d) gametic infertility

a)

If Charles gets married and starts a family, which of the following chromosomal abnormalities has an increased chance of occurring in his children? a) YO b) XO c) YY d) XXY

d

Which of the following types of organisms commonly demonstrates polyploidy? a) fish b) reptiles c) mammals d) flowering plants

d

Which of the following variations of the sentence "Where is the cat?" is most like a chromosomal deletion? a) Where is the the cat? b) Where the is cat? c) Where is cat the the cat? d) Where is cat?

d

In theory, when a nondisjunction for chromosome 18 occurs during meiosis I, four gametes can be produced. If these gametes are fertilized with unaffected gametes from the second parent, what observations would you make concerning the resulting embryos? a) Two of the embryos will be trisomic for chromosome 18, and two will contain a single copy of chromosome 18. b) All four possible embryos will be trisomic for chromosome 18. c) Two of the embryos will be trisomic for chromosome 18, and two will be normal. d) Two of the embryos will be normal, and two will contain a single copy of chromosome 18.

a

Why are individuals with an extra chromosome 21, which causes Down syndrome, more numerous than individuals with an extra chromosome 3 or chromosome 16? a) Extra copies of the other somatic chromosomes are probably fatal. b) There are probably more genes on chromosome 21 than on either chromosomes 3 or 16. c) Nondisjunction of chromosomes 3 and 16 probably occurs more frequently. d) Down syndrome results in more serious symptoms than either trisomy 3 or trisomy 16.

a

Down syndrome can be the result of _____. a) a deletion in chromosome 22 b) occurrence of meiosis without cytokinesis c)nondisjunction of chromosome 21 during meiosis d) deletion of chromosome 21

c

During which stage of meiosis could this nondisjunction have occurred? a) telophase II b) telophase I c) anaphase II d) prophase I

c

On average, what percentage of infants born to 45-year-old mothers have Down syndrome? a) 1% b) 3% c) 8% d) 10% e) 30%

b

Jacobsen syndrome, which can cause heart defects, intellectual deficiencies, and bleeding disorders, is caused by a deletion of the terminal end of chromosome 11. What method could you use to determine whether an individual has Jacobsen syndrome? a) Count the number of chromosomes present. b) Perform a karyotype using a person's white blood cells. c) Look at a person's skin cells in G1 under a light microscope. d) Place a person's red blood cells in culture to see if they grow

b

Polyploidy is involved in which of the following examples? a) XYY males b) A normal watermelon has 22 chromosomes but seedless watermelons have 33 chromosomes. c) XO females d) Some plants alternate between haploid and diploid phas

b

Trisomy for most autosomes is fatal, yet trisomy or even tetrasomy (four copies) of the X chromosome is not. What is the explanation for this difference? a) The X chromosome does not carry any genes. b) Only one copy of the X chromosome is functional, regardless of the total number of X chromosomes. c) There is a mechanism to keep only two X chromosomes functional, regardless of the total number. d) The number of X chromosomes is always balanced by the number of Y chromosomes.

b

Which of the following indicates Turner syndrome? a) XXY b) XO c) XYY d) XXX

b

Which of the following statements regarding Down syndrome is false? a) Trisomy 21 is the cause of Down syndrome. b) Down syndrome is least likely to be seen in the infants of mothers over 40. c) Down syndrome is the most common serious birth defect in the United States. d) People with Down syndrome usually have a shorter life span than normal.

b

Use the graph and your knowledge of Down syndrome to select the three true statements. a) The number of infants born with Down syndrome increases at a steady rate from maternal age 25 to 50. b) The incidence of Down syndrome in infants born to mothers under the age of 35 is less than 0.5%. c) Down syndrome is caused by a trisomy of chromosome 21. d) The risk of having a baby with Down syndrome more than doubles for 45-year old mothers compared to 40-year old mothers. e) The largest five-year increase in the incidence of Down syndrome occurs between the maternal ages of 35 and 40.

b, c, d

How many generations does it take to develop a new plant species by polyploidy? a) 10 b) about 20 c) 1 d) 2

c

If a chromosome fragment breaks off and then reattaches to the original chromosome but in the reverse direction, the resulting chromosomal abnormality is called a(n) a) translocation. b) reciprocal translocation. c) inversion. d) deletion.

c

If these four cells resulted from cell division of a single cell with diploid chromosome number 2n = 4, what best describes what just occurred? a) normal meiosis b) inversion c) nondisjunction d) translocation

c

The exchange of parts between nonhomologous chromosomes is called _____. a) inversion b) transformation c) reciprocal translocation d) crossing over

c

Which of the following statements about nondisjunction is false? a) Women with a single X chromosome have Turner syndrome and are sterile. b) In general, a single Y chromosome is enough to produce "maleness." c) In mammals, extra copies of the Y chromosome are typically inactivated. d) Nondisjunction in meiosis can affect autosomes and sex chromosomes.

c

You are a medical student and are reviewing a case study about a past patient. The patient was 4 feet 8 inches tall at age 38, was unable to have children, and had an above-average intelligence. The patient also had an irregular number of chromosomes. What diagnosis would you give the patient? a) Klinefelter syndrome b) chronic myelogenous leukemia c) Turner syndrome d) Down syndrome

c

Cancer is not usually inherited because a) the causes of cancer are not usually genetic. b) people with cancer usually die before reproducing. c) the cancerous cells usually interfere with the ability to produce gametes. d) the chromosomal changes in cancer are usually confined to somatic cells.

d

You suspect that a serious developmental disorder is due to a chromosome abnormality and prepare a karyotype from an affected individual. In analyzing the karyotype, how could you distinguish trisomy from a chromosome structural defect such as a duplication? a) The chromosome number in both cases would be normal, but in trisomy there would be three chromatids on one chromosome and in a duplication there would be two chromatids on one chromosome. B) The chromosome number in trisomy would be normal; in a duplication, there would be one more chromosome. C) In both cases there would be an extra chromosome, but in trisomy there would be three chromatids on one chromosome and in a duplication there would be two chromatids on one chromosome. D) In trisomy there would be one extra chromosome; in a duplication, the number of chromosomes would be normal, but one chromosome would have two copies of a portion of the chromosome.

d